Super-adsorbing porous thermo-responsive desiccants

ABSTRACT

Thermo-responsive hydrogel composite (TRHC) desiccants having high adsorption capacities, fast adsorption/desorption rates, and low regeneration temperatures (Treg) compared to traditional desiccants. TRHC desiccants may be synthesized by freeze drying. The porous structures resulting from freeze drying copolymers of thermo-responsive polymers and/or hygroscopic agents may be combined with hygroscopic inorganic salts, resulting in TRHC desiccants having superior performance properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 63/074,072 filed on Sep. 3, 2020, the contents of whichare incorporated herein by reference in their entirety.

CONTRACTUAL ORIGIN

This invention was made with government support under Contract No.DE-AC36-08GO28308 awarded by the Department of Energy. The governmenthas certain rights in the invention.

BACKGROUND

Heating, ventilation, and air conditioning (HVAC) equipment may accountfor about 40% of the energy consumed in buildings and is predicted toincrease by approximately 6.2% annually. Solid desiccant airconditioning (SDAC) systems have been proposed as an alternative toconventional vapor compression refrigeration systems (VCRS). Hygroscopicadsorbents or desiccants, with high affinities for water vapor, can beused to control humidity and temperature in buildings when applied indesiccant dehumidification or closed-cycle adsorption heat pumps (AHP).The coefficient of performance (COP) of those technologies isfundamentally limited by the properties of the adsorbent materials(i.e., the desiccants) and their associated heat and mass transfercharacteristics. The low COP in the state of the art AHP systems isprimarily due to the adsorbent bed performance. Typical soliddesiccants, such as silica gels, present a tradeoff between theiradsorption and desorption capability due to their fixed affinity toadsorbates with either low adsorption capacities or high regenerationtemperatures. An ideal absorbent would possess high adsorption capacity(AdC), which is the vapor uptake per unit mass of the solid adsorbent,high adsorption/desorption rate, and low regeneration temperature(T_(reg)). However, incumbent adsorbents have either low AdC or highT_(reg). Thus, there remains a need for improved solid desiccants SDACsystems if significant energy savings are to be made in future HVACsystems and equipment.

SUMMARY

An aspect of the present disclosure is a composition of athermo-responsive desiccant, the composition including athermo-responsive polymer, and a hygroscopic agent, in which thethermo-responsive desiccant has a lower critical solution temperature(LCST) transition, the thermo-responsive desiccant is configured toadsorb a water at a temperature below the LCST transition, and thethermo-responsive desiccant is configured to desorb the water at atemperature above the LCST transition. In some embodiments, a main chainincluding the thermo-responsive polymer is covalently bonded to aplurality of side chains comprised of the hygroscopic agent forming agrafted polymer. In some embodiments, the thermo-responsive polymer isinterlaced with the hygroscopic agent forming an interpenetratingnetwork, and the hygroscopic agent is not covalently bonded to thehygroscopic agent. In some embodiments, the thermo-responsive polymer iscovalently bonded to the hygroscopic agent, resulting in a copolymer. Insome embodiments, the thermo-responsive polymer includes at least one ofpoly(N-isopropylacrylamide) (PNIPAAm), poly[2-dimethylamino]ethylmethacrylate, hydroxypropylcellulose, poly(vinylcaprolactame),poly-2-isopropyl-2-oxazoline, or polyvinyl methyl ether. In someembodiments, the hygroscopic agent comprises an inorganic salt. In someembodiments, the inorganic salt includes at least one of calciumchloride (CaCl₂)), lithium chloride (LiCl), aluminum chloride (AlCl₃),sodium chloride (NaCl), sodium nitrate (NaNO₃), sodium hydroxide (NaOH),potassium nitrate (KNO₃), potassium chloride (KCl), potassium carbonate(K₂CO₃), potassium sulfate (K₂SO₄), a potassium phosphate, potassiumhydroxide (KOH), magnesium chloride (MgCl₂), magnesium nitrate(Mg(NO₃)₂), magnesium sulfate (MgSO₄), magnesium iodide (MgI₂), calciumchloride (CaCl₂)), calcium nitrate (Ca(NO₃)₂), zinc chloride (ZnCl₂),zinc nitrate (ZnNO₃), zinc sulfate (ZnSO₄), iron chloride (FeCl₃),lithium bromide (LiBr), or lithium chloride (LiCl). In some embodiments,the hygroscopic agent includes an organic polyelectrolyte. In someembodiments, the organic polyelectrolyte includes at least one of sodiumacrylate, poly(sodium 4-styrenesulfonate), chlorine-doped polypyrrole(PPy-Cl), a sodium polyacrylate, poly(ethylene oxide), an alginate, or across-linked bipolar polymer. In some embodiments, a crosslinker is alsoincluded. In some embodiments, the crosslinker includes at least one ofN,N′-methylenebisacrylamide (MBAA), N,N′-ethylenebisacrylamide,N,N′-propylenebisacrylamide, polyethylene glycol diacrylate,divinylbenzene (para, ortho, meta), bis(2-methacryloyl)oxyethyldisulfide, 1,4-Bis(4-vinylphenoxy)butane, or triethylene glycoldimethacrylate. In some embodiments, the thermo-responsive desiccant hasan adsorption capacity between about 1.5 g moisture/g composition andabout 4 g moisture/g composition when at a temperature below the LCSTtransition. In some embodiments, the thermo-responsive desiccant has anadsorption rate between greater than 0 g moisture/g composition-hour andabout 3 g moisture/g composition-hour when at a temperature below theLCST transition. In some embodiments, the thermo-responsive desiccanthas a desorption rate between greater than 0 g moisture/gcomposition-hour and about 3 g moisture/g composition-hour when at atemperature above the LCST transition.

An aspect of the present disclosure is a device configured to remove awater from a substantially continuous sheet, the device includes athermo-responsive desiccant, and a drum comprising the thermo-responsivedesiccant, in which the thermo-responsive desiccant includes athermo-responsive polymer, and a hygroscopic agent, in which thethermo-responsive desiccant has a lower critical solution temperature(LCST) transition, the thermo-responsive desiccant is configured toadsorb a water at a temperature below the LCST transition, and thethermo-responsive desiccant is configured to desorb the water at atemperature above the LCST transition, the drum is configured to rotateand direct the substantially continuous sheet through a first zone and asecond zone, while in the first zone, the thermo-responsive desiccant isconfigured to adsorb at least a portion of the water contained in thesubstantially continuous sheet at a temperature below the LCSTtransition, while in the second zone, the thermo-responsive desiccant isconfigured to desorb the water at a temperature above the LCSTtransition, and the water is desorbed in a liquid phase. In someembodiments, the substantially continuous sheet is a paper pulp.

An aspect of the present disclosure is a device configured to remove awater from a granular material, the device including a thermo-responsivedesiccant, a first drum comprising the thermo-responsive desiccant, asecond drum comprising the thermo-responsive desiccant, in which thethermo-responsive desiccant includes a thermo-responsive polymer, and ahygroscopic agent; in which the thermo-responsive desiccant has a lowercritical solution temperature (LCST) transition, the thermo-responsivedesiccant is configured to adsorb a water at a temperature below theLCST transition, and the thermo-responsive desiccant is configured todesorb the water at a temperature above the LCST transition, the firstdrum and the second drum are positioned adjacent to each other to form agap between the first drum and the second drum, the first drum rotatesin a clockwise direction and the second drum rotates in acounterclockwise direction, the gap is configured to receive thegranular material, each drum is configured to be operated at atemperature below the LCST transition while at least in the gap, suchthat at least a portion of the water adsorbed by the thermo-responsivedesiccant and removed from the granular material, each drum isconfigured to rotate to the second zone operated at a temperature abovethe LCST transition, such that the water is desorbed from thethermo-responsive desiccant, and the water is desorbed in the liquidphase. In some embodiments, the granular material comprises a foodproduct.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present disclosure are illustrated in thereferenced figures of the drawings. It is intended that the embodimentsand figures disclosed herein are to be considered illustrative ratherthan limiting.

FIG. 1A illustrates a schematic of an exemplary super-adsorbing, porous,thermo-responsive hydrogel composite (TRHC) desiccant, according to someembodiments of the present disclosure.

FIG. 1B, both Panels A) and B) illustrate a thermo-responsive hydrogelcomposite (TRHC) desiccant, according to some embodiments of the presentdisclosure.

FIG. 2 illustrates an exemplary reaction of a thermo-responsive polymer,a cross-linker, and hygroscopic compound for producing a TRHC desiccant,according to some embodiments of the present disclosure.

FIG. 3 illustrates a schematic diagram of an adsorption heat exchanger(Ad-HEX) that includes TRHC desiccant incorporated into a thermallyconductive metal foam, according to some embodiments of the presentdisclosure.

FIG. 4A illustrates a system utilizing separate sensible and latentcooling (SSLC) air conditioning and cooling, according to someembodiments of the present disclosure.

FIG. 4B illustrates a desiccant wheel and a channel cross-section with acontrol volume for modeling, according to some embodiments of thepresent disclosure.

FIG. 5 illustrates a process flow diagram for an air conditioning systemutilizing a desiccant wheel, according to some embodiments of thepresent disclosure.

FIG. 6 Panel (a) illustrates adsorption/desorption of TRHC desiccants;Panel (b) illustrates a photo of copolymer; and Panel (c) illustrates aphoto of TRHC desiccants, according to some embodiments of the presentdisclosure.

FIG. 7 illustrates a device for drying solid and/or porous films,according to some embodiments of the present disclosure.

FIG. 8 illustrates a device for drying granular solids, according tosome embodiments of the present disclosure.

FIG. 9 illustrates starting water content (x-axis) vs. final watercontent (y-axis) for the TRHC desiccants with a thermo-responsivepolymer of NIPAAm and a hygroscopic agent of NaAlginate at an 8:1 weightratio, according to some embodiments of the present disclosure. Datapoints are according to RPM used: 20,000 RPM, 10,000 RPM, 5,000 RPM,1,000 RPM. An equivalent moisture content line that would indicate nochange between starting and final moisture content (i.e. y=x) isincluded for reference.

FIG. 10 illustrates starting Moisture content (x-axis) vs. finalMoisture content (y-axis) for the TRHC desiccants with athermo-responsive polymer of NIPAAm and a hygroscopic agent ofNaAlginate at an 8:1 weight ratio soaked in CaCl₂) solutions of 2.5 wt %or 5 wt %, according to some embodiments of the present disclosure. Anequivalent moisture content line that would indicate no change betweenstarting and final moisture content (i.e. y=x) is included forreference.

FIG. 11 illustrates centrifuged TRHC desiccants that have a collapsed,opaque structure can be reswollen in water to recover their shape,according to some embodiments of the present disclosure.

FIG. 12 illustrates dynamic vapor sorption curve at 25° C. and finalmoisture contents for a TRHC desiccant constructed of athermo-responsive polymer of NIPAAm and a hygroscopic agent ofNaAlginate at an 8:1 weight ratio soaked in 2.5 wt % CaCl₂) (i.e.,inorganic hygroscopic agent or crosslinker) solutions, according to someembodiments of the present disclosure.

FIG. 13 illustrates dynamic vapor sorption curves at varyingtemperatures and final moisture contents for the TRHC desiccants havinga thermo-responsive polymer of NIPAAm and a hygroscopic agent ofNaAlginate at an 8:1 weight ratio soaked in 5 wt % CaCl₂) solutions,according to some embodiments of the present disclosure.

FIG. 14 illustrates starting moisture content (x-axis) vs. finalmoisture content (y-axis) for a TRHC desiccant constructed of athermo-responsive polymer of NIPAAm, a hygroscopic agent of NaAcrylate,and a hygroscopic agent of NaAlginate at a weight ratio of 1:1:0.25,according to some embodiments of the present disclosure. An equivalentmoisture content line that would indicate no change between starting andfinal moisture content (i.e. y=x) is included for reference

FIG. 15 illustrates vapor sorption of a for a TRHC desiccant constructedof a thermo-responsive polymer of NIPAAm, a hygroscopic agent ofNaAcryl, and a hygroscopic agent of NaAlg desiccant in the environmentalchamber at 95% relative humidity (RH) and 25° C., according to someembodiments of the present disclosure.

FIG. 16 illustrates a representative differential scanning calorimetry(DSC) trace for a TRHC desiccant constructed of a thermo-responsivecomponent of NIPAAm and a hygroscopic agent of Sodium Alginate in an 8:1weight ratio in 5% solution, where a negative heat flow representsenergy flowing into the TRHC desiccants and the DSC is heating from −40°C. to 70° C., according to some aspects of the present disclosure.

FIG. 17 illustrates the onset and peak of the transition temperature fora TRHC desiccant constructed of a thermo-responsive component of NIPAAmand a hygroscopic agent of Sodium Alginate in an 8:1 weight ratio in 5%solution, according to some aspects of the present disclosure.

FIG. 18 illustrates the onset and peak of the transition temperature fora TRHC desiccant constructed of a thermo-responsive component of NIPAAmand a hygroscopic agent of Sodium Alginate in an 8:1 weight ratio in 5%solution, according to some aspects of the present disclosure.

FIG. 19 illustrates the heat flow through the LCST transition for a TRHCdesiccant constructed of a thermo-responsive component of NIPAAm and ahygroscopic agent of Sodium Alginate in an 8:1 weight ratio in 5%solution, according to some aspects of the present disclosure.

FIG. 20 illustrates the chemical structure of an exemplary graftedcopolymer TRHC, according to some aspects of the present disclosure.

FIG. 21 illustrates the performance of a grafted copolymer TRHC at atemperature greater than the lower critical solution temperature (LCST)and above the LCST, according to some aspects of the present disclosure.

FIG. 22 Panel (a) illustrates the performance of a grafted copolymerTRHC; and Panel (b) illustrates the chemical structure of an exemplarygrafted copolymer TRHC in the form of an interpenetrating network,according to some aspects of the present disclosure.

FIG. 23 illustrates a process of making a TRHC in the form of aninterpenetrating network, according to some aspects of the presentdisclosure.

FIG. 24 Panel (a) illustrates the removal of moisture from a paper pulpby a TRHC; and Panel (b) illustrates the vapor sorption rate from apaper pulp by a TRHC, according to some aspects of the presentdisclosure.

REFERENCE NUMERALS

-   -   100 . . . thermo-responsive hydrogel composite (TRHC) desiccant    -   110 . . . thermo-responsive polymer    -   120 . . . crosslinker    -   130 . . . hygroscopic agent    -   300 . . . adsorption heat exchanger    -   310 . . . matrix material    -   400 . . . air conditioning system    -   410 . . . rotating container    -   420 . . . gas inlet stream    -   430 . . . gas outlet stream    -   440 . . . regeneration gas inlet stream    -   450 . . . regeneration gas outlet stream    -   470 . . . water adsorbing zone    -   480 . . . water desorbing zone    -   490 . . . water stream (not shown)    -   491 . . . wall    -   492 . . . TRHC desiccant layer    -   493 . . . volume for gas flow

DETAILED DESCRIPTION

The present disclosure may address one or more of the problems anddeficiencies of the prior art discussed above. However, it iscontemplated that some embodiments as disclosed herein may prove usefulin addressing other problems and deficiencies in a number of technicalareas. Therefore, the embodiments described herein should notnecessarily be construed as limited to addressing any of the particularproblems or deficiencies discussed herein.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, “some embodiments”, etc., indicate that theembodiment described may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to affect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described.

As used herein the term “substantially” is used to indicate that exactvalues are not necessarily attainable. By way of example, one ofordinary skill in the art will understand that in some chemicalreactions 100% conversion of a reactant is possible, yet unlikely. Mostof a reactant may be converted to a product and conversion of thereactant may asymptotically approach 100% conversion. So, although froma practical perspective 100% of the reactant is converted, from atechnical perspective, a small and sometimes difficult to define amountremains. For this example of a chemical reactant, that amount may berelatively easily defined by the detection limits of the instrument usedto test for it. However, in many cases, this amount may not be easilydefined, hence the use of the term “substantially”. In some embodimentsof the present invention, the term “substantially” is defined asapproaching a specific numeric value or target to within 20%, 15%, 10%,5%, or within 1% of the value or target. In further embodiments of thepresent invention, the term “substantially” is defined as approaching aspecific numeric value or target to within 1%, 0.9%, 0.8%, 0.7%, 0.6%,0.5%, 0.4%, 0.3%, 0.2%, or 0.1% of the value or target.

As used herein, the term “about” is used to indicate that exact valuesare not necessarily attainable. Therefore, the term “about” is used toindicate this uncertainty limit. In some embodiments of the presentinvention, the term “about” is used to indicate an uncertainty limit ofless than or equal to ±20%, ±15%, ±10%, ±5%, or ±1% of a specificnumeric value or target. In some embodiments of the present invention,the term “about” is used to indicate an uncertainty limit of less thanor equal to +1%, ±0.9%, ±0.8%, ±0.7%, ±0.6%, +0.5%, ±0.4%, ±0.3%, ±0.2%,or ±0.1% of a specific numeric value or target.

Among other things, the present disclosure relates to thermo-responsivehydrogel composite (TRHC) desiccants having, among other things,relatively high adsorption capacities, relatively fastadsorption/desorption rates, and relatively low regenerationtemperatures (T_(reg)) compared to traditional desiccants. The TRHCdesiccant may be composed of a thermo-responsive polymer and ahygroscopic agent. In some embodiments, the TRHC desiccant may include across linker. The thermo-responsive polymer and the hygroscopic agentmay be connected to form the TRHC in one of three ways: 1) as a graftedcopolymer, 2) as an interpenetrating network, and 3), as a copolymer.

As shown herein, high water adsorption capacities may result from thehygroscopic nature of the polymers and/or inorganic salts. In addition,water desorption rates at low temperatures with small thermal energyrequirements may result from t TRHC desiccants, which become hydrophobicand release water during shrinkage above their “lower critical solutiontemperatures” (LCST), which can range between about −10° C. and about150° C. and can be tuned (i.e., controlled) depending on, among otherthings, the composition of the TRHC desiccant. This results in lowerenergy requirements for regenerating the TRHC desiccants, largely due toa reduction in the enthalpy of vaporization. Fast wateradsorption/desorption rates may be achieved from the engineered porousstructures (e.g., resulting from freeze drying) of the TRHC desiccants.Within buildings, these super-adsorbing TRHC desiccants may be used inair conditioning systems to dehumidify air, within a novel and highcoefficient of performance (COP) adsorption heat pump process, and/orwithin a building envelope to enable moisture storage and release. Thecomposition and systems described herein may also have the potential forapplications beyond buildings, such as harvesting water from air or fromthe industrial drying of films (e.g., paper pulp, food products, etc.).In some embodiments of the present disclosure, the materials describedherein may have applications for controlled moisture storage and/orextraction in building envelopes, energy efficient water harvesting fromair to help mitigate water scarcity, and/or industrial drying of thinfilms.

FIG. 1A illustrates a macroscopic view of an exemplary super-adsorbingporous TRHC desiccant 100, according to some embodiments of the presentdisclosure. The TRHC desiccant 100A on the left illustrates the processof the adsorption of water vapor into the TRHC desiccant and the TRHCdesiccant 100B on the right illustrates the process of desorption ofwater from the TRHC desiccant. FIG. 1B illustrates a molecular view ofan exemplary super-adsorbing porous TRHC desiccant 100, according tosome embodiments of the present disclosure. FIG. 1B illustrates that, ingeneral, a TRHC desiccant 100 may be composed of three constituentparts: a thermo-responsive polymer 110, a crosslinker 120, and ahygroscopic agent 130, where a hygroscopic agent 130 may be an organiccompound 130A and/or an inorganic compound 130B. Panel A) of FIG. 1Billustrates that the components of a TRHC desiccant 100 may be randomlymixed but physically connected via covalent and/or ionic interactions.In some embodiments of the present disclosure, in addition to covalentand ionic bonds, the various components of a TRHC desiccant 100 mayinteract via hydrogen bonding, van der Waals forces, and/or other chargeinteractions.

An example of a thermo-responsive polymer 110 ispoly(N-isopropylacrylamide) (PNIPAAm). Examples of inorganic hygroscopicagents 130B include inorganic salts, such as calcium chloride (CaCl₂)),lithium chloride (LiCl), and/or lithium bromide (LiBr), whereas examplesof organic hygroscopic agents 130A include organic polyelectrolytes suchas sodium acrylate, poly(sodium 4-styrenesulfonate), PPy-Cl(chlorine-doped polypyrrole), sodium polyacrylates, alginates, and/orcross-linked bipolar [—NR³⁺ and —SO³⁻] polymers. In some embodiments ofthe present disclosure, a TRHC desiccant can be constructed of a doublenetwork thermo-responsive polymer, composed of, for example, PNIPAMhydrogel and an alginate gel. Among other things, an alginate gel may beused to improve the mechanical strength of the resultant TRHCdesiccants. Further examples of thermo-responsive polymers 110 includepoly[2-dimethylamino]ethyl methacrylate, poly(vinylcaprolactame), andpolyvinyl methyl ether. The molecular structure of sodium alginate, anorganic hygroscopic agent 130A with inorganic hygroscopic agents 130B,Al³⁺ and CaCl₂), as well as a thermo-responsive polymer 110, PNIPAM, ina resin network due to the use of a crosslinker 120,N,N′-methylenebisacrylamide (MBAA). This resin structure also includesan inorganic hygroscopic agent, calcium chloride (CaCl₂)). The structureof PPy-Cl is shown below as Structure 1:

In general, there are at least two types of crosslinkers, where oneconnects different polymer chains through covalent bonds, and the otherthrough ionic bonds. In some embodiments of the present disclosure,where a TRHC desiccant 100 is constructed of a thermo-responsive polymer110 and an inorganic hygroscopic agent 130B (e.g., a salt), acrosslinker 120 may be used to crosslink the thermo-responsive polymer110 to form a thermo-responsive gel. In some embodiments this may resultin an interpenetrating network. An interpenetrating network (orinterpenetrating polymer network) is a network made of two or morepolymers which are at least partially interlaced on a polymer scale, butnot covalently bonded together. In some embodiments, an interpenetratingnetwork may result from a thermo-responsive polymer being at leastpartially interlaced with a hygroscopic agent. In some embodiments ofthe present disclosure, where a TRHC desiccant is constructed of athermo-responsive polymer 110 and an organic hygroscopic agent 130A(e.g., a polyelectrolyte), a crosslinker may be used to crosslink atleast one of thermo-responsive polymer 110 and/or the organichygroscopic agent 130A (e.g., a polyelectrolyte). An example of across-linker is MBAA to crosslink thermo-responsive polymer 110. Anothercrosslinker is calcium chloride (CaCl₂)), which both ionicallycrosslinks organic hygroscopic agent 130A and acts as an inorganichygroscopic agent.

In some embodiments, a TRHC desiccant may be synthesized, which has botha high adsorption capacity (AdC) (approximately 10× higher thansecondary organic aerosol (SOA) solid desiccants, (e.g., silica gels)and a low T_(reg) (less than about 50° C.). In some embodiments, a TRHCdesiccant may be synthesized by freeze-drying at least onethermo-responsive polymer with at least one hygroscopic agent, resultingin a porous polymeric desiccant having the physical properties andperformance metrics of a TRHC desiccant. In some embodiments of thepresent disclosure, TRHC desiccants may be synthesized by freeze drying.Freeze drying, also known as lyophilization or cryodesiccation, is a lowtemperature dehydration process that involves freezing the product,lowering pressure, then removing the ice by sublimation. It is a waterremoval process typically used to preserve material structures. Asdescribed herein, freeze drying may be used to remove moisture (i.e.,water) contained inside desiccants and/or the materials used tosynthesize desiccants to create porous structures for enhanced masstransfer. In some embodiments of the present disclosure, the porousstructures resulting from freeze drying copolymers of thermo-responsivepolymers and/or hygroscopic agents may be combined with hygroscopicinorganic salts, resulting in TRHC desiccants having superiorperformance properties.

A hygroscopic agent may have a sufficiently high ionic strength (e.g.,greater than approximately 0.1 M) to enable it to behave like a vapordrawing agent during adsorption. In some embodiments of the presentdisclosure, a thermo-responsive polymer may drastically change itsaffinity to water upon phase transition at its LCST, resulting in ashrinkage in the material and a release of water to facilitate fastdesorption at a relatively low T_(reg) above its LCST (see FIG. 1A).

One example of a TRHC desiccant composed of thermo-responsive polymerand organic hygroscopic agent is illustrated in FIG. 2 . First, athermo-responsive monomer, N-isopropylacrylamide (NIPAAm), and anorganic hygroscopic agent, sodium acrylate (SA), are reacted with acrosslinker, MBAA, using an initiator, ammonium persulfate (APS), atabout 70° C. for a period of time between 6 hours and 12 hours. This mayresult in a copolymer structure for the TRHC. This copolymer structuremay be mixed with an additional hygroscopic agent, such as aluminumchloride (AlCl₃). A molecular view of the copolymer structure with AlCl₃is also shown in FIG. 2 . Alternatively, the TRHC desiccant can besynthesized while below the LCST by reaction of NIPAAm, MBAA, and APSwith an accelerator, such as tetramethylethylenediamine (TEMED), at roomtemperature (approximately 25° C.) for a period of time between about 1minute and about 24 hours. In this example, the resultant crosslinkedcopolymer was freeze dried overnight to remove the water and form thefinal targeted, porous TRHC desiccant. As illustrated in FIG. 2 , theresultant TRHC copolymer may reversibly switch between a firsttransparent hydrophilic state (below the LCST) to a second opaquehydrophobic state (above the LCST), corresponding to the adsorption ofwater and the desorption of water, respectively.

As described herein, a study was completed where a thermo-responsivematerial content, hygroscopic agents' (e.g., inorganic ones and/ororganic ones) chemical nature and contents, and synthesis conditionswere varied to study their effects on, among other things, AdC.Exemplary TRHC desiccants were identified that achieve a targetadsorption capacity of at least 4 g/g (water adsorbed/desiccant), whichis 10 times higher than SOA solid desiccants such (e.g., silica gel) andhaving a T_(reg) of about 50° C. or less, which would allow these TRHCdesiccants to utilize over 75% of the currently available industrialwaste heat at below about 100° C. generated in the United States. Insome embodiments of the present disclosure, the T_(reg) may be tuned toa range between about 0° C. and about 100° C., depending on theapplication, by adjusting the composition of the TRHC desiccantsconstituents, e.g., thermo-responsive polymers, crosslinkers, and/orhygroscopic agents.

In some embodiments of the present disclosure, a TRHC desiccant canadsorb between about 0.5 g/g and about 1.0 g/g (moistureadsorbed/desiccant) at about 200° C. at 70% relative humidity (RH). Insome embodiments of the present disclosure, a TRHC desiccant may have anAdC between about 1.5 g/g and about 4 g/g (moisture adsorbed/desiccant)at about 20° C. at 98% relative humidity (RH). In some embodiments ofthe present disclosure, a TRHC desiccant may have an AdC of at least 0.5g/g (moisture adsorbed/desiccant), a high adsorption rate (of at least0.5 g/g-hour at 20° C. at 70% RH), and a high desorption rate (of atleast 0.4 g/g-hour at 50° C. at 30% RH). In some embodiments of thepresent disclosure, a TRHC desiccant may be stable and provide reliableperformance, even when repeatedly cycled between a first adsorbed stateand a second desorbed state as described above (see FIG. 1A) (greaterthan 95% performance retention after 10 cycles). In some embodiments ofthe present disclosure, a TRHC desiccant may have an AdC of at least 1.5g/g (moisture adsorbed/desiccant), a high adsorption rate (of at least1.0 g/g-hour), and a high desorption rate (of at least 1.2 g/g-hour). Insome embodiments of the present disclosure, a TRHC desiccant may includea hybrid adsorbent that has a stable, reliable performance, even whenrepeatedly cycled (greater than 95% performance retention after 100cycles).

In some embodiments of the present disclosure, a porous structure (e.g.resulting from freeze drying process) may be incorporated into a TRHCdesiccant to relieve the mechanical stresses that may be present duringadsorption/desorption cycling, which may allow water vapor to moreeasily access the inner mass and/or surface areas of the TRHC desiccantand/or induce capillary condensation (which can occur at mesoporousscales between about 2 nm and about 50 nm). Freeze-drying may be used tocreate a microporous and/or nanoporous structure in TRHC desiccants bycontrolling the processing parameters (e.g., freezing temperature andduration). As described herein, a heat and mass transfer model has beenused to optimize the porous structure of TRHC desiccants for highadsorption/desorption kinetics (in some instances two times higher thanSOA solid desiccants). Among other things, results from this model havevalidated that the use of a porous structure can relieve the mechanicalstresses during hydration/dehydration cycling and can allow water vaporto access the inner part of the composite more easily. In someembodiments of the present disclosure, a porous structure withnanometer-scale to micrometer-scale pore sizes may be manufactured byusing a polymeric porogen.

In some embodiments of the present disclosure, a TRHC desiccant asdescribed herein may minimize the evaporation of water duringregeneration, which is necessary in traditional desiccants (e.g., silicagel). By releasing the adsorbed moisture in the liquid phase, due to theunique LCST phase transition initialized by low-grade thermal energy,the heat of vaporization of water from liquid to vapor is avoided andhigh COP values can be obtained. A further aspect of the presentdisclosure are devices and/or systems that utilize TRHC desiccants asdescribed herein, some of which are described in detail below.

In some embodiments of the present disclosure, a hygroscopic polymer(acrylic acid) may be obtained from biomass-derived sources. Utilizingacrylic acid and other biomass-derived monomers may result in lowermanufacture energies and carbon dioxide emissions in the finalmanufacture of the polymer. In some embodiments of the presentdisclosure, a precursor proposed in a route for manufacturing a TRHCdesiccant may be obtained from the esterification of acrylic acid withamines to from a thermos-responsive materials and diamines to form across-linker. A high degree of customization is available, and polymersmay be modified pre- or post-polymerization.

The following paragraphs provide more extensive lists of the componentsthat may be utilized and/or combined to synthesized TRHC desiccants 100,as described herein.

Thermo-responsive polymers 110 may include a polymer that includes afunctional group that includes at least one of an amide, amethacrylate/acrylate, and/or an ether. In some embodiments of thepresent disclosure, such a functional group may be paired with at leastone of a hydrophobic group and/or aliphatic group. In some embodimentsof the present disclosure, a thermo-responsive polymer 110 may includeat least one of poly(N-isopropylacrylamide) (PNIPAM) and/or a PNIPAMderivative. PNIPAM derivatives include (LCSTs shown in brackets)poly(N-n-propylacrylamide) (PNNPAM) (10° C.),poly(N-cyclopropylacrylamide) (PNCPAM) (53° C.),poly(N,N-diethylacrylamide) (PDEAM) (33° C.),poly(N-(NO-isobutylcarbamide)propyl methacrylamide) (PiBuCPMA) (13° C.),poly(N-(2-methoxy-1,3-dioxan-5-yl) methacrylamide) (PNMM) (22° C.),poly(N-vinylisobutyramide) (PNVIBA) (39° C.), poly(N-vinyl-n-butyramide)(PNVBA) (32° C.), poly(N-acryloylpyrrolidine) (PAPR) (51° C.),poly(N-(NO-ethylcarbamido)propyl methacrylamide) (PiBuCPMA) (50-57° C.),poly(N-(1-hydroxymethyl)propylmethacrylamide) (PHMPMA) (30-34° C.),poly[N-(2,2-dimethyl-1,3-dioxolane)methyl] acrylamide (PDMDOMA) (23°C.), poly([N-(2,2-dimethyl-1,3-dioxolane)methyl]acrylamide-co-[N-(2,3-dihydroxyl-n-propyl)] acrylamide) (23-49° C.),poly(N-(2-ethoxy-1,3-dioxan-5-yl) methacrylamide) (PNEM) (52° C.),poly(N-(2,2-di-methyl-1,3-dioxan-5-yl) methacrylamide) (PNDMM) (15° C.),poly(N-(2,2-di-methyl-1,3-dioxan-5-yl) acrylamide) (PNDMA), copolymer ofN-isopropylmethacrylamide and a methacrylamide monomer with labilehydrazone linkages (13-44° C.),poly(trans-N-(2-ethoxy-1,3-dioxan-5-yl)acrylamide) (PtNEA) (13.7-17.5°C.), and poly(N-acryloyl-NO-propylpiperazine) (PNANPP) (37° C.).

In some embodiments of the present disclosure, a thermo-responsivepolymer 110 may include a ring system such as poly(N-vinylcaprolactam)(PVCa) (32° C.) and/or poly(N-vinylpyrrolidone) (PVPy) (30° C.). In someembodiments of the present disclosure, a thermo-responsive polymer 110may include a methacrylate and/or a methacrylate complex such as atleast one of poly[N-(2-methacryloyloxyethyl) pyrrolidone] (PNMP) (52°C.), Poly(N-ethylpyrrolidine methacrylate) (PEPyM) (15° C.),poly(dimethylaminoethyl methacrylate) (PDMAEMA) LCST=14-50° C.,poly(methacrylamide) (PMAAm) (57° C.), poly(2-(2-methoxyethoxy)ethylmethacrylate) (PMEO2MA) (26° C.),poly(2-[2-(2-methoxyethoxy)ethoxy]ethyl methacrylate) (PMEO3MA) (52°C.), poly(oligo(ethylene glycol) methacrylate (POEGMA) (60-90° C.),poly([oligo(2-ethyl-2-oxazoline) methacrylate]-co-(methyl methacrylate))(35-80° C.), poly(N-acryloyl-1-proline methyl ester) poly(A-Pro-OMe)(15-20° C.), poly(N-acryloyl-L-valine NO-methylamide) (PAVMA) (6-19°C.),Poly(N-isopropylacrylamide)-b-poly[3-(N-(3-methacrylamidopropyl)-N,N-dimethyl)ammoniopropanesulfonate] (PNIPAM-b-PSPP) (9-19° C.), poly(N-acryloylglycinamide)(PNAGA) (22-23° C.), and/or poly(N-acryloylasparaginamide) (PNAAAM)(4-28° C.).

In some embodiments of the present disclosure, a thermo-responsivepolymer 110 may include an acrylate such as at least one ofpoly[(di(ethylene glycol) ethyl ether acrylate)-co-(oligoethylene glycolacrylate)] (P(DEGA-co-OEGA) (15-90° C.) and/orpoly(2-hydroxypropylacrylate) (PUPA) (30-60° C.). In some embodiments ofthe present disclosure, a thermo-responsive polymer 110 may include apolyether such as at least one of poly(ethylene oxide) (85° C.),poly(propylene oxide) (0-50° C.), poly(ethoxyethyl glycidal ether)(30-40° C.), and/or poly(glycidol-co-glycidol acetate) (4-100° C.). Insome embodiments of the present disclosure, a thermo-responsive polymer110 may include a styrene such as poly(4-vinylbenzylmethoxytetrakis(oxyethylene)ether) (39° C.). In some embodiments of thepresent disclosure, a thermo-responsive polymer 110 may include aphosphazene such as at least one ofpoly[bis((ethoxyethoxy)ethoxy)phosphazene] (PBEEP) (38° C.) and/orpoly[bis(2,3-bis(2-methoxyethoxy)propanoxy) phosphazene] (PBBMEPP) (38°C.). In some embodiments of the present disclosure, a thermo-responsivepolymer 110 may include a vinyl ether such as at least one ofpoly(methyl vinyl ether) (PMVE) poly(2-(2-ethoxy)ethoxyethyl (35-36°C.), poly(2-(2-ethoxy)ethoxyethyl vinyl ether) (PEOEOVE) (41° C.),and/or poly(2-methoxyethyl vinyl ether) (PMOVE) (70° C.). In someembodiments of the present disclosure, a thermo-responsive polymer 110may include an oxazoline such as at least one ofpoly(2-ethyl-2-oxazoline) (PEOx) (62-65° C.),poly(2-isopropyl-2-oxazoline) (PiPOx) (36° C.), and/orpoly(2-n-propyl-2-oxazoline) (PnPOx) poly([oligo(2-ethyl-2-oxazoline)(36° C.). In some embodiments of the present disclosure, athermo-responsive polymer 110 may include an oxazine such as at leastone of poly(2-ethyl-2-oxazine) (PEtOZI) (11-13° C.) and/orpoly(2-n-propyl-2-oxazine) (PnPropOZI) (56° C.).

In some embodiments of the present disclosure, a thermo-responsivepolymer 110 may include at least one ofpoly(endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid,bis[2-[2-(2-ethoxyethoxy)ethoxy]ethyl] ester) (25° C.), oligo(ethyleneoxide)-grafted polylactide (19-27° C.), P(Val-Pro-Gly-Val-Gly) (27° C.),Val-Pro-Gly-Val-Gly and oligo(ethylene glycol) grafted polynorbornene(16-30° C.), Val-Pro-Gly-Val-Gly derived polymethacrylate (15-55° C.),derivatives of poly(N-substituted a/b-asparagine) (25-100° C.), ethyland butyl modified polyglycine (20-60° C.), PEG-ylated poly-L-glutamate(30-57° C.), poly(vinyl alcohol-co-vinyl acetal) (P(VOH-co-VAc)) (17-41°C.), butyl glycidyl ether modified starch (5-33° C.), and/orPoly(acrylonitrile-co-acrylamide) (P(An-co-AM)) (6-60°.

In some embodiments of the present disclosure, a crosslinker 120 mayinclude at least one of a chemical crosslinker and/or a physicalcrosslinker. Examples of chemical crosslinkers includeN,N′-methylenebisacrylamide (MBAA), N,N′-ethylenebisacrylamide,N,N′-propylenebisacrylamide, polyethylene glycol diacrylate,divinylbenzene (para, ortho, meta), bis(2-methacryloyl)oxyethyldisulfide, 1,4-Bis(4-vinylphenoxy)butane, and/or triethylene glycoldimethacrylate. In some embodiments of the present disclosure, acrosslinker may include a non-divinyl crosslinker such as at least oneof a crosslinker resulting from converting acrylic acid to hydrazine andreacting the hydrazine with vinyl aldehyde, a crosslinker resulting fromthe copolymerization of styrene in the presence of UV radiation, Fe₃O₄nanoparticles, phytic acid, and/or an N-hydroxysuccinimide) derivativesuch as at least one of disuccinimidyl suberate, bis(sulfosuccinimidyl)suberate, and/or N-(Allyloxycarbonyloxy)succinimide.

Examples of physical crosslinkers include various salts such as at leastone of an aluminum salt, a calcium salt, an alkaline earth metal salt,and/or a Group III salt. In some embodiments of the present disclosure,a physical crosslinker may include at least one of aluminum chloride,phosphate, sulfate, fluoride, bromide, iodide, nitrate, hydroxide, andother salts that produce the aluminum cation, calcium chloride,phosphate, sulfate, fluoride, bromide, iodide, nitrate, hydroxide,and/or any other salt that produces an aluminum cation. In someembodiments of the present disclosure, a physical crosslinker mayinclude a salt that includes at least one of beryllium, magnesium,strontium, barium, radium chloride, boron, gallium, indium, and/orthallium chloride.

In some embodiments of the present disclosure a hygroscopic agent 130may include at least one of an organic hygroscopic agent and/or aninorganic hygroscopic agent. In some embodiments of the presentdisclosure, a physical crosslinker and an organic hygroscopic agent maybe substantially the same material. In some embodiments, a physicalcrosslinker may also serve as an organic hygroscopic agent. In someembodiments of the present disclosure, an organic hygroscopic agent mayinclude at least one of an acetate, a nitrate, and/or a polymerincluding at least one an acrylate, a sulfonate, a hydroxyl group, acarboxylate, and/or an ammonium cation. In some embodiments of thepresent disclosure, an organic hygroscopic agent may include at leastone of sodium alginate, poly(pyrrole), and/or poly(pyrrole) doped withan inorganic ion, such as chloride, bromide, sulfate, sulfonate,hydroxide, and/or phosphate. In some embodiments of the presentdisclosure, an organic hygroscopic agent may include at least one ofpotassium acetate, sodium acetate, ammonium nitrate, poly(sodiumacrylate), poly(styrene sulfonates), a modified cellulose compounds(e.g. cellulose sulfonate), a poly(vinyl alcohol), a polyamide, and/or apolymer containing an ammonium cation.

In some embodiments of the present disclosure, an inorganic hygroscopicagent may be a salt. Examples of inorganic salt hygroscopic agentsinclude at least one of lithium chloride (LiCl), calcium chloride(CaCl₂)), aluminum chloride (AlCl₃), sodium chloride (NaCl), sodiumnitrate (NaNO₃), sodium hydroxide (NaOH), potassium nitrate (KNO₃),potassium chloride (KCl), potassium carbonate (K₂CO₃), potassium sulfate(K₂SO₄), a potassium phosphate, potassium oxide (KOH), magnesiumchloride (MgCl₂), magnesium nitrate (Mg(NO₃)₂), magnesium sulfate(MgSO₄), magnesium iodide (MgI₂), calcium chloride (CaCl₂)), calciumnitrate (Ca(NO₃)₂), zinc chloride (ZnCl₂), zinc nitrate (ZnNO₃), zincsulfate (ZnSO₄), iron chloride (FeCl₃), lithium bromide (LiBr), and/orlithium chloride (LiCl).

In some embodiments of the present disclosure, an LCST desiccant asdescribed herein may be utilized in an adsorption heat exchanger(Ad-HEX) 300, as shown in FIG. 3 . For example, an adsorption heatexchanger 300 may include coating a TRHC desiccant 100 into a matrixmaterial 310 as shown in FIG. 3 . In some embodiments of the presentdisclosure, a matrix material 310 may be thermally conductive tomaximize the heat transfer rates of adsorption heat exchanger 300. Forexample, a matrix material 310 may include a metal foam having asubstantial pore volume, which may be filled at least partially with theTRHC desiccant 100. In some embodiments of the present disclosure,energy for desorbing the water adsorbed in the TRHC desiccants may beprovided by low-grade waste heat. In some embodiments of the presentdisclosure, an air conditioning system may include an Ad-HEX 300 thatincorporates a TRHC desiccant as described herein, resulting in a systemhaving, among other things, enhanced heat and mass transfer performance.In some embodiments of the present disclosure, an Ad-HEX 300 maydemonstrate little, if any, delamination of a TRHC desiccant coatingpositioned on a flat metal surface after 100 cycles, resulting in 100%gel volume expansion and shrinkage during each cycle. In someembodiments of the present disclosure, an Ad-HEX 300 may include aporous TRHC desiccant having a desirable pore size range (e.g., between100 nm to 1,000) and porosity range (e.g., between 10 vol % and about 70vol %) and cycling stability of greater than 90% performance retentionafter 10 cycles.

In some embodiments of the present disclosure, an air conditioningsystem may include a TRHC desiccant positioned on and/or in a rotatingwheel, which may be combined with at least one of a VCRS and/or anevaporative cooler to form a hybrid separate sensible and latent cooling(SSLC) air conditioning system (see FIGS. 4A and 4B). In someembodiments of the present disclosure, a desiccant-containing, rotatingwheel may efficiently remove moisture from the air (latent load) whilethe VCRS or evaporative cooler may reduce the air temperature (sensibleload), or vice versa. Such a SSLC arrangement may eliminate therequirement that an air conditioning system be operating below the dewpoint temperature of the supply air, which includes use of a coolingcoil and subsequent reheating. The low T_(reg) and low energyrequirement of TRHC desiccants described herein may enable the use ofcondenser heat or low-grade building waste heat, which may improvesystem efficiency and/or reduce system complexity compared to currentSDAC systems. FIG. 4A illustrates a schematic of hybrid SSLC airconditioning system, according to some embodiments of the presentdisclosure. The air conditioning system may circulate a refrigerantthrough a condenser, expansion valve, evaporator, and a compressor. Thesupply air is the air to be pulled in from the ambient (i.e., externalto the building) and cooled and dehumidified using the TRHC desiccant(i.e., water from the supply air is absorbed by the TRHC desiccant whenthe TRHC desiccant is below the LCST). The regeneration air may be warmair from the interior of the building (which may further be heated by asupplemental heater) to heat the TRHC desiccant above the LCST,resulting in the absorbed water being desorbed. This may be said to“regenerate” the TRHC desiccant (i.e., cause it to desorb previouslyabsorbed water to prepare for future additional absorption).

FIG. 4B provides more details of an air conditioning system 400 thatincludes a rotating container 410 (e.g., a rotating wheel), according tosome embodiments of the present disclosure. Referring to the left panelof FIG. 4B, a rotating container 410 may be in the form of a rotatingcontainer 410 for a TRHC desiccant 100 for contacting the TRHC desiccant100 with a water-containing gas inlet 420 stream to produce adehumidified conditioned gas outlet stream 430. In some embodiments ofthe present disclosure, a rotating container 410 may have a circularshape, i.e. the shape of a wheel, although other shapes fall within thescope of the present disclosure. This may be accomplished by positioninga first portion of the TRHC desiccant 100 in a water adsorbing zone 470of the container 410 that enables contacting the gas inlet stream 420with the TRHC desiccant 100, resulting in the removal of water vaporfrom the gas inlet stream 420 to produce the dehumidified gas outletstream 430. Once the TRHC desiccant has adsorbed sufficient moisture,e.g. at or close to its AdC, the container 410 may be rotated around acentral axis, x-axis, resulting in the movement of the first portion ofTRHC desiccant 100 out of the water adsorbing zone 470 into a waterdesorbing zone 480. Once in the water desorbing zone 470, thewater-containing TRHC desiccant 100 may be contacted with a regenerationgas inlet stream 440 that provides the energy needed to heat the TRHCdesiccant to its LCST resulting in the removal of the adsorbed waterfrom the TRHC desiccant 100, such that it can be rotated back into thewater adsorbing zone 470 to repeat the cycle. Referring again to FIG.4B, once the regeneration gas has provided the energy needed to desorbthe water from the TRHC desiccant 100, it may exit the container 410 asa slightly cooler but humid regeneration gas outlet stream 450. Theliquid water may then be removed from the container 410 as a wateroutlet stream 490 (not shown).

Referring again to the right panel of FIG. 4B, in the example shown, thecontainer 410 is rotated and the gas streams are fixed in position. Insome embodiments of the present invention, the container 410 may bemaintained in a fixed position, i.e. does not rotate, and the variousgas streams (e.g. 420-450) may be moved to different locations aroundthe container 410, as needed.

Referring to the right panel of FIG. 4B, a rotating container 410 may beconstructed of an outer supporting wall 491 structure, where the wall490 forms an internal surface bounding an internal space forming one ormore channels. In some embodiments of the present disclosure, a TRHCdesiccant 100 may be applied to at least a portion of the internalsurface, forming a layer 492 of the TRHC desiccant. In some embodimentsof the present disclosure this TRHC desiccant layer 492 may beincorporated into a matrix material 310 that is positioned on theinternal surface of the wall 491. At least a portion of the internalspace may be configured for the gas streams directed to the container410. This is space is referred to herein as a volume for gas flow 493.

Thus, a wheel (i.e. container 410) may constantly rotate through twoseparate gas streams—a gas inlet stream 420 which is dried by the TRHCdesiccant 100, and a hot regeneration gas inlet stream 440, whichregenerates the desiccant. In some embodiments of the presentdisclosure, a desiccant-coated rotating wheel (i.e., container 410) maystand alone for energy-efficient dehumidification in industrial and/orcommercial buildings. In some embodiments of the present disclosure, adesiccant-coated rotating wheel (i.e. container 410) may be combinedwith other cooling systems to form a hybrid SSLC A/C system. Asdescribed herein, a desiccant wheel (i.e., container 410) mayefficiently remove moisture from the air (latent load), while thecooling system reduces the air temperature (sensible load). Thisarrangement can eliminate the low dew point temperature requirement ofthe cooling coil and subsequent reheating in VCRS systems.

In some embodiments of the present disclosure, to promote the heattransfer rate, a desiccant wheel (i.e. container 410) may be 3D printedusing a thermally conductive filament with high effective thermalconductivity. TRHC desiccants 100 may be synthesized and coated onto the3D-printed desiccant wheel via chemical bonding by anchoring organicfunctional group onto the surface of desiccant structure or thin filmpaste. In some examples, the container 410 surface will be firstoxidized and then modified and/or further derived to generate ananchored long-chain polymer network. Such a network can form strongbonds with the TRHC desiccant, which may be confirmed by peeling tests.Other suitable chemistry may be used to anchor a TRHC desiccant to asurface with examples including the use of dopamine-functionalizedpolymers and/or the combination of gold with thiol functional groups.These methods for anchoring a TRHC desiccant to a surface are providedfor illustrative purposes and other chemistries fall within the scope ofthe present disclosure.

In some embodiments of the present disclosure, a desiccant-containing, arotating wheel (i.e., container 410) may be operated at different spinspeeds (e.g., rotations per minute (RPM)), which may alter theefficiency of liquid removal of adsorbed moisture from a TRHC desiccant.In some embodiments of the present disclosure, ultrasonic vibrations maybe utilized to avoid evaporation and remove the water in liquid phase,minimizing the energy associated with the enthalpy of vaporization. Theactual percentage of liquid removal may determine the improvement of theCOP of dehumidification and SSLC air conditioning systems. For example,utilizing a TRHC desiccant in a desiccant wheel as shown in FIGS. 4A-B,the COP of SSLC air conditioning systems may be improved by up to fivetimes compared with traditional SOA SDAC systems by achieving up to 90%water removal achieved during regeneration cycles, because thiseliminates 90% of the energy associated with enthalpy of vaporization.

In some embodiments of the present disclosure, utilizing a TRHCdesiccant in a desiccant wheel as shown in FIGS. 4A-B may provide highperformance characteristics under extremely humid conditions and thepotential to use approximately 50-80% less energy than traditional VCRSby removal of the adsorbed moisture (between about 50 wt % and about 90wt %) in liquid form. The TRHC desiccants described herein may also beused for industrial dehumidification because they are less corrosivethan liquid desiccants.

FIG. 5 illustrates a flow diagram of an air conditioning system 400,showing both the flow of mass and energy, according to some embodimentsof the present disclosure. In some embodiments of the presentdisclosure, a system 400 described herein may have a smaller unit sizedue to higher AdC and lower energy-costs for regeneration, compared toincumbent technologies. A comparable COP of an SSLC air conditioningsystem with VCRS for all climates, especially humid conditions, mayenable the renovation of the current air conditioning market. In someembodiments of the present disclosure, a hybrid SSLC air conditioningsystem may include a TRHC desiccant-coated rotary wheel (i.e. container410) and evaporative cooler and/or traditional vapor compression, asshown in FIG. 5 . A desiccant wheel may efficiently remove the moisturefrom the air and a cooler and/or vapor compression air conditioningsystem may remove only sensible heat. This type of arrangement mayremove the need for low evaporator temperatures below the air dewpoint,and subsequently reheating of the air. Additionally, only one-third ofthe energy used by traditional air conditioning systems may be required,leading to a higher COP.

A further benefit to the embodiments described herein is that all theprecursors proposed for at least one synthetic route for manufacturing aTRHC desiccant can be easily obtained from the esterification of acrylicacid with amines/diamines to form thermo-responsive polymers. Initialstudies of this TRHC desiccant synthesis showed the TRHC desiccanthaving a high adsorption capacity of 1.1 g/g (approximately three timeshigher than that of silica gel) (see Panel (a) of FIG. 6 ), therebyoffering the potential to reduce the size of a hybrid SSLC airconditioning by three times. Moreover, TRHC desiccants can beregenerated by discharging the adsorbed moisture in liquid form at a lowtemperature of 50° C., which requires only one third of the energycompared to that of silica gel-based systems for significantly improvingthe COP of hybrid systems (expected to be greater than two).

In addition to removing moisture from the air, a TRHC desiccant may beused for drying solid materials containing liquid water, such as solidsheets (e.g., substantially planar pulps) and films of granular objects(e.g., food products such as dog food or dry cereal). In these examples,the composition may remain the same or additionally include ahygroscopic agent to offer enhanced driving force to absorb liquid wateras TRHC desiccants. A hygroscopic agent may include polyelectrolytes(e.g., poly(sodium styrene sulfonate)) or inorganic materials (e.g.,lithium chloride, LiCl) and may exhibit a high osmotic pressure.

FIG. 7 shows an example of how a substantially continuous sheet (e.g., aplanar material) could be dried. In step 1, the wet sheet comes incontact with a rotating cylinder that is coated with a TRHC. As thecylinder rotates, water is absorbed from the wet sheet into the TRHC andis released as a dry product in step 2. In step 2, the TRHC has becomewet from adsorbing the liquid water and is heated in step 3 to inducethe LCST behavior, which releases the water as a liquid in step 4. TheTRHC is then exposed to air and new wet material to lower thetemperature below the LCST and begin the process again. This process mayalso include additional cooling (e.g. contact with a heat exchanger orcooled air) between steps 4 and 1 to induce a more rapid LCST phasechange. A thin, porous film of non-active material, called the“non-stick layer” is used to prevent tearing/delamination of the TRHCfrom the cylinder to the product, as the gels may be sticky. Thenon-stick layer can be made of any material that does not stronglyadhere to the product Examples of components of the non-stick layerinclude polypropylene and/or polyethylene. This system offers anadvantage over traditional film-drying techniques, which remove waterfrom solid films by evaporation, as water is removed and released in theliquid phase, thereby avoiding the heat of vaporization for water.Therefore, the energy efficiency of drying can be dramatically improvedusing this technique. Additionally, the water released by the TRHC maybe recovered for other uses.

FIG. 8 shows an example of how granular materials (e.g., food) may bedried using a TRHC, in a similar method to FIG. 7 . Wet granularmaterial is first brought into contact with a rotating cylinder (drumdrier), which sorbs liquid water from the granular material into theTRHC. While rotating and drying, the granular material will stick tosurface of the cylinder through adhesive forces. Near the top of thecylinder, a blade is put into contact with the dried food to physicallyremove it from the cylinder, where it is collected in a container belowthe blade or cylinder.

It is important to develop practical methods to facilitate liquid waterrelease from TRHC desiccants having low LCSTs for expansion ofapplications for this class of materials, specifically indehumidification and atmospheric water harvesting. In heated air, TRHCdesiccants can exhibit contraction and expulsion of water to itssurface, but an additional driving force is necessary to overcome thecapillarity/cohesion that holds desorbed water within the porousnetwork. Through adequate removal of desorbed water, the moisturecontent of the TRHC desiccant can be reduced to a point at which a newsorption cycle of humid air can begin. As described herein,centrifugation provides the driving force to separate loosely bound,desorbed water from a TRHC desiccant.

Two methods are described herein to introduce moisture to the TRHCdesiccants to test the ability of centrifugation to remove any adsorbedwater: (1) immersion in DI water and (2) vapor sorption in an RHcontrolled environmental chamber. For the immersion method, TRHCdesiccants were immersed in deionized water for periods of seconds tohours depending on the water uptake kinetics specific to that TRHCdesiccant (dictating factors include porosity and hydrophilicity) anddesired moisture content of the TRHC desiccant. When the appropriatemoisture content is achieved, the TRHC desiccants were removed from thewater where excess surface moisture was removed by dabbing surfaces witha lint-free Kimwipe™ prior to weighing and subsequent centrifugation.

For the vapor sorption method, the TRHC desiccants were incubated in anenvironmental chamber at the appropriate relative humidity andtemperature. In the experiments described herein, a relative humidity of95% and temperature of 25° C. was used. Sorption proceeded until thedesired moisture content was achieved. In cases of TRHC desiccants thatincluded hygroscopic salts (e.g., calcium chloride CaCl₂)), excesscondensation may occur outside of the TRHC desiccant and were notconsidered in the moisture content determination.

A Beckman Coulter Optima XE-90 (the Optima L100XP was used in the 7Gseries of experiments) ultracentrifuge using an SW-32 rotor capable of amaximum of 32,000 RPM (approximately 175,000 g-force at the extremity)and a minimum of 1,000 RPM (approximately 170 g-force at the extremity)was used to complete the experiments described herein (see Table 1).Temperature controls allowed for ranges of 0° C. to 40° C. and the timeof each run could be set from one minute up to 1000 hours. In theexperiments detailed here, the range of RPMs explored was 1,000-20,000,temperatures from 10° C.-40° C., and times of 5-30 min. An additionalindependent control variable was the height of TRHC desiccant placementwithin the centrifuge tube. The specific conditions that yielded optimumresults are discussed below.

TABLE 1 Example of g-force as a function of tube depth at 1000 RPMLength down g-force at tube (cm) 1000 RPM 0 71.0 1 82.2 2 93.4 3 104.5 4115.7 5 126.9 6 138.1 7 149.3 8 160.4 8.9 170.5

Depending on the hydrated nature of the TRHC desiccant, it may adhere tothe plastic centrifuge tube (31 mL Beckman Coulter thick wallpolycarbonate tubes, in this case). This allowed the TRHC desiccant tobe secured at varying heights within the tube. In this report, if theTRHC desiccants exhibited adhesive properties, placement against theside wall was approximately halfway down the length of the tube. Thisadhesion is advantageous for (1) keeping the TRHC desiccant separatedfrom the desorbed water that collects at the bottom and (2) reducing theg-force exposure of the TRHC desiccants through proximity to therotational axis. The approximate g-force that the TRHC desiccantsexperienced can be calculated by measuring the distance of the TRHCdesiccant from the top of the tube and adding the distance to the centerof the rotor and using those values in the following equation:g _(force)=1.118×10⁻⁵(L _(rotor) +L _(tube))(RPM)²where L_(rotor) is the distance (in cm) from the central axis to the topof the tube (6.35 cm for the SW-32 rotor), L_(tube) is the distance fromthe top of the tube, and RPM is the set rotations per minute. g-force asa function of depth of tube is shown in Table 1. Too high of arotational speed can shear the TRHC desiccants off the wall, but withlow speeds (1000 RPM) all shear failures can be avoided. Placing theTRHC desiccant at the bottom of the tube (or if it falls as a result ofovercoming the adhesion forces) can still allow for water release andphase separation if the temperature is above the LCST. There ispotential for the TRHC desiccant to resorb some of the expelled waterduring the deceleration of the centrifuge, so adhesion to the side wallof the centrifuge tube, if possible, is desired.

Initially, higher speeds (in the range of about 5,000 RPM to about20,000 RPM) were used, but as shown in FIG. 9 , this was determined tobe unnecessary as the minimum speed of 1,000 RPM proved to provide morethan enough force to remove desorbed water from the TRHC desiccants. Inan application setting, these lower required forces would directlytranslate to less energy expenditure to spin out water. Additionally,after determining that TRHC desiccant placement higher up in the tubefacilitated separation from desorbed water, rotation speeds above 1,000RPM caused the TRHC desiccant to shear down the wall of the tube, oftencausing tearing in the TRHC desiccant. Therefore, speeds of less thanabout 1,000 RPM were preferred. For example, speeds in the range ofabout 500 to about 900 RPM may be used.

Temperatures above the anticipated LCST appeared provide good waterrelease. In these experiments, the set point of the centrifuge wasprimarily approximately 40° C., but heating was slow due to heating onlytaking place when the chamber was sealed and under vacuum. Often, themost achievable temperature was about 38° C. and an acceptable minimumfor starting the centrifuge was chosen to be approximately 35° C. (asidefrom experiments where a lower temperature was the goal). Thesetemperatures were acceptable for water release in these experiments. Inone experiment, sample 7A was spun at about 20,000 RPM at about 21° C.for about 30 min (the most aggressive conditions used) and spread out tocover the bottom of the tube with no water release, indicating thathigher temperatures were required. With a sample containing CaCl₂), andattached to the sidewall, sample 14F(2) (shown in FIG. 10 ), was spun at1,000 RPM for about 30 min at about 25.5° C. and actually releasedwater, but had a higher final moisture content than any of the calciumchloride (CaCl₂)) containing TRHC desiccants spun at greater than about35° C. for half the time, indicating that there was still an influenceof temperature for these samples.

Time periods between about 5 minutes and about 30 minutes were exploredfor water release. The primary factor dictating the spin time washypothesized to be temperature equilibration of the TRHC desiccant andtube to the elevated temperature of the centrifuge chamber to allow forwater release. The ambient temperature of the lab was measured to bebetween about 21° C. and about 22° C. and the centrifuge chamber wasprimarily set to about 40° C. Time periods of about 5 minutes and about10 minutes did not appear to allow for adequate equilibration of theTRHC desiccant and there was limited or no water release. In the caseswhere water was released after about 10 minutes of centrifugation, themoisture content was higher than those centrifuged for between about 15minutes and about 30 minutes (except for sample 7F(2) in FIG. 9centrifuged at 10,000 RPM). Durations of 15 minutes were determined tobe optimal for good water release at the shortest time.

Results of water release from samples with a thermo-responsive polymerof poly(N-isopropylacrylamide) and a hygroscopic agent of sodiumalginate (NaAlg) in an 8:1 ratio. These TRHC desiccants had moderatesorption times between about 10 minutes to about 60 minutes yielding amoisture content of between about 4 g_(water)/g_(gel) and about 10g_(water)/g_(gel). This was the primary set where the centrifugationconditions were optimized, as shown by the large number of samples inFIG. 9 . These TRHC desiccants were extremely adhesive when swollen andproved difficult to handle without tearing or losing mass to surfaces(e.g., gloves, weigh paper, forceps, centrifuge tube). Increasingtransparency and volume expansion with moisture sorption was observed,followed by complete opacity and structural collapse when centrifuged.When placed back into DI water, the collapsed TRHC desiccants couldregenerate into their flat, square shapes shown in FIG. 11 , indicatingthe force applied through centrifugation was not enough to causenoticeable damage, at least by this test.

For samples of a thermo-responsive polymer of NIPAAm and a hygroscopicagent of NaAlg in an 8:1 ratio with a crosslinker of calcium chloride(CaCl₂)), these TRHC desiccants had very fast immersion sorption times,often on the order of less than 10 seconds for moisture contents of 4g_(water)/g_(gel). The precipitated CaCl₂) within the porous structurewas leached out during the sorption and release phase, resulting in massreductions of about 30% to about 40% when dried after testing. Formoisture content calculations, the final mass had to be used to accountfor the salt leaching. Among the salt impregnated TRHC desiccants,samples 16A and 16B were the only set of TRHC desiccants that wereplaced into the environmental chamber at about 25° C. and about 95% RH(as shown in FIG. 10 ). All others absorbed water from immersion intodeionized water. The starting moisture contents for the vapor sorptionsamples were much lower than the immersion sorption samples as a resultof the adsorbed water in the environmental chamber dissolving out theCaCl₂) and forming a solution separate from the TRHC desiccant whichcould not be resorbed. Despite the leaching of the salts, there wasstill a small amount of water release when centrifuged, lowering themoisture content from about 1.3 g_(water)/g_(gel) to about 0.9g_(water)/g_(gel).

In FIG. 12 and FIG. 13 , the final moisture contents from thecentrifuged 2.5% and 5% TRHC desiccants in solution are plotted ashorizontal lines over their respective dynamic vapor sorption curves.This provides information about the range of RH environments where theseTRHC desiccants could uptake enough water that could then be releasedvia centrifugation. The 5% TRHC desiccants would require an operatingenvironment of at least 80% RH at room temperature to absorb enoughmoisture to release it as liquid water. For the 2.5% TRHC desiccants,that operating RH is even higher. The high threshold for vapor sorption,coupled with the CaCl₂) leaching restricts both applicability andcyclability in the context of a desiccant wheel.

For examples of a thermo-responsive polymer of NIPAAm, a hygroscopicagent of sodium acrylate (NaAcryl) and a crosslinker of NaAlg in a ratioof 1:1:0.25, this set of TRHC desiccants exhibited very slow immersionsorption times, where after 2 hours of immersion, only a moisturecontent of about 1.7 g_(water)/g_(gel) was achieved, shown in FIG. 14 .This composition of TRHC desiccants appeared to have a higher density,smaller porous structure than the TRHC desiccants without sodiumacrylate, which is hypothesized to have restricted sorption kinetics.Even at low starting moisture contents, a portion of the absorbed watercould be spun out of the TRHC desiccant using the optimized conditions(1,000 RPM, approximately 38° C., 15 min) to a moisture content betweenabout 0.8 g_(water)/g_(gel) to about 1 g_(water)/g_(gel). Whenconditioned at about 95% RH and about 25° C. in the environmentalchamber, shown in FIG. 15 , these TRHC desiccants adsorb less than about0.4 g_(water)/g_(gel) meaning that they would require an additionalhygroscopic component to increase the adsorbed moisture content to apoint where they could exhibit liquid water release.

FIGS. 16-19 illustrate differential scanning calorimetry (DSC) data forTRHC desiccants constructed of a thermo-responsive polymer of NIPAAm anda hygroscopic agent of NaAlg in an 8:1 ratio in a 5% solution, accordingto some embodiments of the present disclosure. A DSC measures the heatinput required to cause a change in temperature, therefore endothermicand exothermic transitions can be measured. FIG. 16 illustrates arepresentative DSC trace for these samples, where a negative heat flowrepresents energy flowing into the sample and the DSC is heating fromabout −40° C. to about 70° C. From this trace, the melting of water canbe seen at approximately about −5° C. and the LCST transition can beseen at approximately 20° C. Because these samples contain CaCl₂), theLCST transition is suppressed from the normal about 32° C. due to theHofmeister effect.

As with most PNIPAM samples, the LCST transition also depends on theconcentration of polymer, or, in other words, the LCST is dependent onthe water content of the gel. This phenomenon can be seen in FIGS. 17and 18 , where the same gel's onset and peak of the transitiontemperature were respectively measured at different water uptakes. Theonset temperature is measured as the intercept of the maximum of theslope of the peak and the baseline determined by the non-peak region.The peak temperature is simply the maximum of the magnitude of the peak(in this case, the minimum of the peak). For contrast, a PNIPAM controlgel that is about 90% water is shown in FIG. 19 , exhibiting thetraditional approximately 32° C. transition temperature. The freezing ofwater can be seen by a large peak at approximately 0° C. and the insethighlights the LCST transition at approximately 32° C.

FIG. 20 illustrates the chemical structure of an exemplary gratedcopolymer TRHC 100, according to some aspects of the present disclosure.In FIG. 20 , the thermo-responsive polymer 110 is PNIPAM and thehygroscopic agent 130 is poly(sodium acrylate) (PSA). The TRHC 100 maybe referred to as PNIPAM-g-PSA (i.e., PNIPAM grafted to PSA). For agrafted polymer structure of a TRHC, there may be primary backbone ofthe thermo-responsive polymer 110 and side chains of the hygroscopicagent 130 may extend of that primary backbone. The side chains may becovalently bonded to the primary backbone. A grafted copolymer TRHC mayalso be referred to as a graft polymer TRHC.

FIG. 21 illustrates the performance of a grafted copolymer TRHC k at atemperature greater than the lower critical solution temperature (LCST)and above the LCST, according to some aspects of the present disclosure.As shown in FIG. 21 , when the temperature surrounding the graftedcopolymer TRHC 100 is below the LCST (left), the grafted copolymer TRHC100 may perform in a substantially hydrophilic way and be capable ofabsorbing water into the grafted copolymer TRHC 100. The water may beabsorbed by filling the empty space within the structure, as shown inFIG. 21 . When the temperature surrounding the grafted copolymer TRHC100 is above the LCST (right), the grafted copolymer TRHC 100 mayperform in a substantially hydrophobic way and be capable of desorbingwater out of the grafted copolymer TRHC 100. The water may be desorbedby the compressing of the structure, as shown in FIG. 21 .

FIG. 22 Panel (a) illustrates the performance of a grafted copolymerTRHC; and Panel (b) illustrates the chemical structure of an exemplarygrafted copolymer TRHC, according to some aspects of the presentdisclosure. In Panel (a) of FIG. 22 , the graph shows that the wateruptake by the grafted copolymer TRHC 100 increased as the relativehumidity increased at every temperature. In Panel (b) of FIG. 22 , anexemplary grafted copolymer TRHC 100 is shown. In this example, thethermo-responsive polymer 110 is PNIPAM and the hygroscopic agent 130 ispoly (ethylene oxide) (PEO).

FIG. 23 illustrates a process of making a TRHC in the form of aninterpenetrating network, according to some aspects of the presentdisclosure. First, an initial network of acrylic acid,azobisisobutyronitrile (AIBN) and N,N′-methylenebisacrylamide (MBAA) wascreated by being heated to about 50° C. and maintained at thattemperature for approximately 24 hours. This is then soaked inapproximately 0.1 M sodium hydroxide (NaOH) for approximately 24 hours,resulting in the hygroscopic agent 130 (PSA in this example). Next, PSAmay be soaked in at least one of NIPAM, ammonium persulfate (APS), orMBAA to form the thermo-responsive polymer 110. To have thethermo-responsive polymer 110 and hygroscopic agent 130 intertwine(i.e., chemically crosslink), they may be heated to approximately 50° C.for approximately 24 hours. This results in the thermo-responsivepolymer 110 and the hygroscopic agent 130 being intertwined by notactually chemically bonded together.

FIG. 24 Panel (a) illustrates the removal of moisture from a paper pulpby a TRHC; and Panel (b) illustrates the vapor sorption rate from apaper pulp by a TRHC, according to some aspects of the presentdisclosure. The removal of moisture from a paper pulp may be done usingsystem as shown in FIG. 7 . Panel (a) shows the expected evaporation(i.e., the paper mass resulting from natural evaporation) compared tothe actual moisture loss (by the difference in mass of the paper pulp)using the TRHC. Using the TRHC and the system in FIG. 7 , the mass ofthe paper pulp may be reduced, indicating a large amount of moisturebeing removed from the paper pulp. Panel (b) shows the expected vaporsorption (i.e., the natural weight of the TRHC with little to knowmoisture being absorbed) compared to the increase in polymer mass as aresult from the absorption of moisture from the paper pulp.

EXAMPLES

Example 1. A composition of a thermo-responsive desiccant, thecomposition comprising: thermo-responsive polymer; and a hygroscopicagent; wherein: the thermo-responsive desiccant has a lower criticalsolution temperature (LCST) transition, the thermo-responsive desiccantis configured to adsorb a water at a temperature below the LCSTtransition, and the thermo-responsive desiccant is configured to desorbthe water at a temperature above the LCST transition.

Example 2. The composition of Example 1, wherein: a main chaincomprising the thermo-responsive polymer is covalently bonded to aplurality of side chains comprised of the hygroscopic agent forming agrafted polymer.

Example 3 The composition of Example 1, wherein: the thermo-responsivepolymer is interlaced with the hygroscopic agent forming aninterpenetrating network, and the hygroscopic agent is not covalentlybonded to the hygroscopic agent.

Example 4. The composition of Example 1, wherein: the thermo-responsivepolymer is covalently bonded to the hygroscopic agent, resulting in acopolymer.

Example 5. The composition of Example 1, wherein the thermo-responsivepolymer comprises at least one of poly(N-isopropylacrylamide) (PNIPAAm),poly[2-dimethylamino]ethyl methacrylate, hydroxypropylcellulose,poly(vinylcaprolactame), poly-2-isopropyl-2-oxazoline, or polyvinylmethyl ether.

Example 6. The composition of Example 1, wherein the hygroscopic agentcomprises an inorganic salt.

Example 7. The composition of Example 6, wherein the inorganic saltcomprises at least one of calcium chloride (CaCl₂)), lithium chloride(LiCl), aluminum chloride (AlCl₃), sodium chloride (NaCl), sodiumnitrate (NaNO₃), sodium hydroxide (NaOH), potassium nitrate (KNO₃),potassium chloride (KCl), potassium carbonate (K₂CO₃), potassium sulfate(K₂SO₄), a potassium phosphate, potassium hydroxide (KOH), magnesiumchloride (MgCl₂), magnesium nitrate (Mg(NO₃)₂), magnesium sulfate(MgSO₄), magnesium iodide (MgI₂), calcium chloride (CaCl₂)), calciumnitrate (Ca(NO₃)₂), zinc chloride (ZnCl₂), zinc nitrate (ZnNO₃), zincsulfate (ZnSO₄), iron chloride (FeCl₃), lithium bromide (LiBr), orlithium chloride (LiCl).

Example 8. The composition of Example 1, wherein the hygroscopic agentcomprises an organic polyelectrolyte.

Example 9. The composition of Example 8, wherein the organicpolyelectrolyte comprises at least one of sodium acrylate, poly(sodium4-styrenesulfonate), chlorine-doped polypyrrole (PPy-Cl), a sodiumpolyacrylate, poly(ethylene oxide), an alginate, or a cross-linkedbipolar polymer.

Example 10. The composition of Example 1, further comprising acrosslinker.

Example 11. The composition of Example 10, wherein the crosslinkercomprises at least one of N,N′-methylenebisacrylamide (MBAA),N,N′-ethylenebisacrylamide, N,N′-propylenebisacrylamide, polyethyleneglycol diacrylate, divinylbenzene (para, ortho, meta),bis(2-methacryloyl)oxyethyl disulfide, 1,4-Bis(4-vinylphenoxy)butane, ortriethylene glycol dimethacrylate.

Example 12. The composition of Example 1, wherein the LCST transition isbetween about −10° C. and about 150° C.

Example 13. The composition of Example 1, wherein the LCST transitionmay be adjusted by adding additional thermo-responsive polymer to thethermo-responsive desiccant.

Example 14. The composition of Example 1, wherein the LCST transition bybe adjusted by adding additional hygroscopic agent to thethermo-responsive desiccant.

Example 15. The composition of Example 1, wherein: the thermo-responsivedesiccant has an adsorption capacity between about 1.5 g moisture/gcomposition and about 4 g moisture/g composition when at a temperaturebelow the LCST transition.

Example 16. The composition of Example 15, wherein: thethermo-responsive desiccant has a performance retention of at least 95%of the adsorption capacity after at least 100 cycles of alternating thetemperature of the thermo-responsive desiccant above and below the LCSTtransition.

Example 17. The composition of Example 1, wherein: the thermo-responsivedesiccant has an adsorption rate between greater than 0 g moisture/gcomposition-hour and about 3 g moisture/g composition-hour when at atemperature below the LCST transition.

Example 18. The composition of Example 1, wherein: the thermo-responsivedesiccant has a desorption rate between greater than 0 g moisture/gcomposition-hour and about 3 g moisture/g composition-hour when at atemperature above the LCST transition.

Example 19. A device configured to remove a water from an air stream,the device comprising: a thermo-responsive desiccant; and a containercomprising the thermo-responsive desiccant; wherein: thethermo-responsive desiccant comprises: thermo-responsive polymer; and ahygroscopic agent; wherein: the thermo-responsive desiccant has a lowercritical solution temperature (LCST) transition, the thermo-responsivedesiccant is configured to adsorb a water from the air stream at atemperature below the LCST transition, and the thermo-responsivedesiccant is configured to desorb the water at a temperature above theLCST transition, the container is configured to rotate through a firstzone and a second zone, while in the first zone, the thermo-responsivedesiccant is configured to adsorb at least a portion of the watercontained in the air stream at a temperature below the LCST transition,while in the second zone, the thermo-responsive desiccant is configuredto desorb the water at a temperature above the LCST transition, and thewater is desorbed in a vapor phase.

Example 20. The device of Example 19, wherein: the container isconfigured to receive a heat in the second zone.

Example 21. The device of Example 20, wherein: the heat is at least oneof a condenser heat or a building waste heat.

Example 22. A device configured to remove a water from a substantiallycontinuous sheet, the device comprising: a thermo-responsive desiccant;and a drum comprising the thermo-responsive desiccant; wherein: thethermo-responsive desiccant comprises: thermo-responsive polymer; and ahygroscopic agent; wherein: the thermo-responsive desiccant has a lowercritical solution temperature (LCST) transition, the thermo-responsivedesiccant is configured to adsorb a water at a temperature below theLCST transition, and the thermo-responsive desiccant is configured todesorb the water at a temperature above the LCST transition, the drum isconfigured to rotate and direct the substantially continuous sheetthrough a first zone and a second zone, while in the first zone, thethermo-responsive desiccant is configured to adsorb at least a portionof the water contained in the substantially continuous sheet at atemperature below the LCST transition, while in the second zone, thethermo-responsive desiccant is configured to desorb the water at atemperature above the LCST transition, and the water is desorbed in aliquid phase.

Example 23. The device of Example 22, wherein the substantiallycontinuous sheet is a paper pulp.

Example 24. A device configured to remove a water from a granularmaterial, the device comprising: a thermo-responsive desiccant; a firstdrum comprising the thermo-responsive desiccant; a second drumcomprising the thermo-responsive desiccant; wherein: thethermo-responsive desiccant comprises: thermo-responsive polymer; and ahygroscopic agent; wherein: the thermo-responsive desiccant has a lowercritical solution temperature (LCST) transition, the thermo-responsivedesiccant is configured to adsorb a water at a temperature below theLCST transition, and the thermo-responsive desiccant is configured todesorb the water at a temperature above the LCST transition, the firstdrum and the second drum are positioned adjacent to each other to form agap between the first drum and the second drum, the first drum rotatesin a clockwise direction and the second drum rotates in acounterclockwise direction, the gap is configured to receive thegranular material, each drum is configured to be operated at atemperature below the LCST transition while at least in the gap, suchthat at least a portion of the water adsorbed by the thermo-responsivedesiccant and removed from the granular material, each drum isconfigured to rotate to the second zone operated at a temperature abovethe LCST transition, such that the water is desorbed from thethermo-responsive desiccant, and the water is desorbed in the liquidphase.

Example 25. The device of Example 24, wherein: the granular materialcomprises a food product.

Example 26. A device configured to remove a water from an air stream,the device comprising: a thermo-responsive desiccant; and a matrixmaterial comprising the thermo-responsive desiccant; wherein: thethermo-responsive desiccant comprises: thermo-responsive polymer; and ahygroscopic agent; wherein: the thermo-responsive desiccant has a lowercritical solution temperature (LCST) transition, the thermo-responsivedesiccant is configured to adsorb a water at a temperature below theLCST transition, and the thermo-responsive desiccant is configured todesorb the water at a temperature above the LCST transition, the matrixmaterial comprises a metal foam having a pore volume, at least a portionof the pore volume is filled with the thermo-responsive desiccant, thematrix material is configured to contact the air stream, and the wateris desorbed in the liquid phase.

The foregoing discussion and examples have been presented for purposesof illustration and description. The foregoing is not intended to limitthe aspects, embodiments, or configurations to the form or formsdisclosed herein. In the foregoing Detailed Description for example,various features of the aspects, embodiments, or configurations aregrouped together in one or more embodiments, configurations, or aspectsfor the purpose of streamlining the disclosure. The features of theaspects, embodiments, or configurations may be combined in alternateaspects, embodiments, or configurations other than those discussedabove. This method of disclosure is not to be interpreted as reflectingan intention that the aspects, embodiments, or configurations requiremore features than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment, configuration, oraspect. While certain aspects of conventional technology have beendiscussed to facilitate disclosure of some embodiments of the presentinvention, the Applicants in no way disclaim these technical aspects,and it is contemplated that the claimed invention may encompass one ormore of the conventional technical aspects discussed herein. Thus, thefollowing claims are hereby incorporated into this Detailed Description,with each claim standing on its own as a separate aspect, embodiment, orconfiguration.

What is claimed is:
 1. A composition of a thermo-responsive desiccant, the composition comprising: a thermo-responsive polymer comprising N-isopropylacrylamide (NIPAAm); a hygroscopic agent comprising sodium acrylate (SA); and a crosslinker comprising N,N′-methylenebisacrylamide (MBAA); wherein: the thermo-responsive desiccant has a lower critical solution temperature (LCST) transition, the thermo-responsive desiccant is configured to adsorb a water at a temperature below the LCST transition, the thermo-responsive desiccant is configured to desorb the water at a temperature above the LC ST transition, and the LCST transition is approximately 50° C.
 2. The composition of claim 1, wherein: a main chain comprising the thermo-responsive polymer is covalently bonded to a plurality of side chains comprised of the hygroscopic agent forming a grafted polymer.
 3. The composition of claim 1, wherein: the thermo-responsive polymer is interlaced with the hygroscopic agent forming an interpenetrating network, and the hygroscopic agent is not covalently bonded to the hygroscopic agent.
 4. The composition of claim 1, wherein: the thermo-responsive polymer is covalently bonded to the hygroscopic agent, resulting in a copolymer.
 5. The composition of claim 1, wherein the thermo-responsive polymer further comprises at least one of poly[2-dimethylamino]ethyl methacrylate, hydroxypropylcellulose, poly(vinylcaprolactame), poly-2-isopropyl-2-oxazoline, or polyvinyl methyl ether.
 6. The composition of claim 1, wherein the hygroscopic agent further comprises an inorganic salt.
 7. The composition of claim 6, wherein the inorganic salt comprises at least one of calcium chloride (CaCl₂), lithium chloride (LiCl), aluminum chloride (AlCl₃), sodium chloride (NaCl), sodium nitrate (NaNO₃), sodium hydroxide (NaOH), potassium nitrate (KNO₃), potassium chloride (KCl), potassium carbonate (K₂CO₃), potassium sulfate (K₂SO₄), a potassium phosphate, potassium hydroxide (KOH), magnesium chloride (MgCl₂), magnesium nitrate (Mg(NO₃)₂), magnesium sulfate (MgSO₄), magnesium iodide (MgI₂), calcium chloride (CaCl₂), calcium nitrate (Ca(NO₃)₂), zinc chloride (ZnCl₂), zinc nitrate (ZnNO₃), zinc sulfate (ZnSO₄), iron chloride (FeCl₃), lithium bromide (LiBr), or lithium chloride (LiCl).
 8. The composition of claim 1, wherein the hygroscopic agent further comprises at least one of poly(sodium 4-styrenesulfonate), chlorine-doped polypyrrole (PPy-Cl), a sodium polyacrylate, poly(ethylene oxide), an alginate, or a cross-linked bipolar polymer.
 9. The composition of claim 1, wherein the crosslinker further comprises at least one of N,N′-ethylenebisacrylamide, N,N′-propylenebisacrylamide, polyethylene glycol diacrylate, divinylbenzene (para, ortho, meta), bis(2-methacryloyl)oxyethyl disulfide, 1,4-Bis(4-vinylphenoxy)butane, or triethylene glycol dimethacrylate.
 10. The composition of claim 1, wherein: the thermo-responsive desiccant has an adsorption capacity between about 1.5 g moisture/g composition and about 4 g moisture/g composition when at a temperature below the LCST transition.
 11. The composition of claim 1, wherein: the thermo-responsive desiccant has an adsorption rate between greater than 0 g moisture/g composition-hour and about 3 g moisture/g composition-hour when at a temperature below the LCST transition.
 12. The composition of claim 1, wherein: the thermo-responsive desiccant has a desorption rate between greater than 0 g moisture/g composition-hour and about 3 g moisture/g composition-hour when at a temperature above the LCST transition.
 13. A device configured to remove a water from a substantially continuous sheet, the device comprising: a thermo-responsive desiccant; and a drum comprising the thermo-responsive desiccant; wherein: the thermo-responsive desiccant comprises: a thermo-responsive polymer comprising N-isopropylacrylamide (NIPAAm); a hygroscopic agent comprising sodium acrylate (SA); and a crosslinker comprising N,N′-methylenebisacrylamide (MBAA); wherein: the thermo-responsive desiccant has a lower critical solution temperature (LCST) transition, the thermo-responsive desiccant is configured to adsorb a water at a temperature below the LCST transition, the thermo-responsive desiccant is configured to desorb the water at a temperature above the LCST transition, the LCST transition is approximately 50° C., the drum is configured to rotate and direct the substantially continuous sheet through a first zone and a second zone, while in the first zone, the thermo-responsive desiccant is configured to adsorb at least a portion of the water contained in the substantially continuous sheet at a temperature below the LCST transition, while in the second zone, the thermo-responsive desiccant is configured to desorb the water at a temperature above the LC ST transition, and the water is desorbed in a liquid phase.
 14. The device of claim 13, wherein the substantially continuous sheet is a paper pulp.
 15. A device configured to remove a water from a granular material, the device comprising: a thermo-responsive desiccant; a first drum comprising the thermo-responsive desiccant; a second drum comprising the thermo-responsive desiccant; wherein: the thermo-responsive desiccant comprises: a thermo-responsive polymer comprising N-isopropylacrylamide (NIPAAm); a hygroscopic agent comprising sodium acrylate (SA); and a crosslinker comprising N,N′-methylenebisacrylamide (MBAA); wherein: the thermo-responsive desiccant has a lower critical solution temperature (LCST) transition, the thermo-responsive desiccant is configured to adsorb a water at a temperature below the LCST transition, the thermo-responsive desiccant is configured to desorb the water at a temperature above the LCST transition, the LCST transition is approximately 50° C., the first drum and the second drum are positioned adjacent to each other to form a gap between the first drum and the second drum, the first drum rotates in a clockwise direction and the second drum rotates in a counterclockwise direction, the gap is configured to receive the granular material, each drum is configured to be operated at a temperature below the LCST while at least in the gap, such that at least a portion of the water adsorbed by the thermo-responsive desiccant and removed from the granular material, each drum is configured to rotate and direct the substantially continuous sheet through a first zone and a second zone, while in the first zone, the thermo-responsive desiccant is configured to adsorb at least a portion of the water contained in the substantially continuous sheet at a temperature below the LCST, while in the second zone, the thermo-responsive desiccant is configured to desorb the water at a temperature above the LCST, each drum is configured to rotate to the second zone operated at a temperature above the LCST, such that the water is desorbed from the thermo-responsive desiccant, and the water is desorbed in the liquid phase.
 16. The device of claim 15, wherein: the granular material comprises a food product. 